[Quinic acid lactone in coffee]

Quinic acid and its lactone (quinide) have been determined in coffee by capillary gas chromatography. No quinide could be detected in 14 green coffee's. After steaming of 4 green coffee's the content of quinic acid was always higher, but no quinide had been formed. During roasting, the latter can be detected when roasting loss exceed 6.5%. It increases approximately proportionally with quinic acid and amounts to 50% of the latter at 22% roasting loss. Both constituents decrease at unusual high roasting loss. In 13 commercial blends of roast coffee 2.4-6.4 g/kg quinide and 8.7-16.6 g/kg quinic acid were present. Especially high values were found in one Espresso type blend and high values in steamed and decaffeinated coffee's. In 11 commercial coffee extracts 2.0-23.2 g/kg quinide and 24.6-36.4 g/kg quinic acid were determined. At higher extraction yield, more quinic acid and quinide is formed, but at very high extraction yield the content of quinide is diminished. During holding of coffee brews at elevated temperature, quinide is slowly hydrolysed.